1. Field of the Invention
The present invention relates to techniques for efficiently generating an application which runs for the navigation among objects contained in an object-oriented database.
2. Description of the Related Art
One of the features of an object-oriented database (ODB) is the function of navigation. This function establishes relations among objects contained in the database, so that links (relational attributes) generated by the established relations can be pursued. By way of example, the specified item of each instance of an object A has the object identifier of each instance of an object B prestored therein, whereby when the object A has been accessed, the object B can be subsequently accessed. As a more concrete example, let's consider a case where the No. information of commodities and the price information thereof are stored in the object A, while the photograph information of the commodities is stored in the object B. In this case, when an instance corresponding to a specified commodity contained in the object A has been accessed, the photograph of the specified commodity can be easily taken out by subsequently accessing the object B.
Heretofore, in order to realize the navigation among objects contained in a database, a system administrant having a special ability has directly described and programmed desired navigational operations with a specified database query language such as SQL (Structured Query Language).
In order to utilize such a prior-art technique, however, the usage of the database query language must be mastered. Therefore, general end users difficulty of utilizing the prior-art technique as stated above, and they have been unable to readily realize the navigation among the objects within the database.
Proposed for coping with such a problem is a technique wherein the navigation among the objects contained in the database is realized using a GUI (Graphical User Interface). With this technique, the end user can pursue the links of the objects graphically displayed on a screen, while successively clicking the links with a mouse for example. Thus, he/she can realize the interactive navigation searching for the object within the database.
In such navigation based on the GUI, however, the links are usually pursued one by one. The reason therefor is that, in a case where the links are set in multilevel fashion among the plurality of objects, such information items as follows are dependent upon users or applications:
How far the links are continuous? PA1 Which object the user of the GUI wants to pursue as a link goal? PA1 Where the navigation is stopped in case of an endless loop (or a recursive loop) formed by the links themselves?
To interactively pursue the links one by one in search of the object within the database in this manner, is very effective when developing an application by the method of trial and error and for learning the structure and contents of the database. However, in a case where the utilization of the navigational function employing the GUI is intended for developing an efficient application in which an accessibility to the database and good use of database resources are taken into consideration, especially a point-to-point service application, the results of the navigation are not directly reflected in the program contents of the application. This poses the problem that the navigational function employing the GUI cannot serve as an effective tool for the application development.